DETROIT -- An attorney for two women
opposing Michigan's ban on gay
marriage urged a judge Tuesday to
halt the treatment of same-sex couples as "second-class citizens,"
the latest in a series of marriage-equality
challenges across the country.

Lawyers delivered opening statements
in a trial that targets a 2004 state
constitutional amendment that recognizes marriage
only between a man and a woman. Two Detroit-area nurses, April DeBoer and Jayne
Rowse, claim the amendment violates their rights under the Equal Protection
Clause of the U.S. Constitution.

The issue: Is there a legitimate state
interest in restricting marriage to a
man and a woman?

Federal judges in recent weeks have
struck down gay marriage bans
in Utah, Oklahoma and Virginia. At least 17 states and the District of Columbia
now allow marriage by same-sex couples.
The Michigan trial, which could last two weeks, will have
testimony from experts in areas of economics, marriage
and child-rearing.

"Nothing says family like a marriage license," DeBoer told reporters
before entering the Detroit federal courthouse hand-in-hand with Rowse, her
partner of eight years.

They walked past more than a dozen
people who marched quietly on the sidewalk with signs declaring, "We
support traditional marriage. One
man, one woman."

Their attorney, Carole Stanyar, said
she would present evidence to show there's no rational basis to single out gays and lesbians who want to marry - a key
legal standard in the case.

"We would like this to be the
last trial in America where same-sex
parents will have to defend themselves," she told U.S. District Judge
Bernard Friedman.

She urged him at the end of trial to strike down Michigan's law and declare "there are no
second-class citizens in this country."

The case began in 2012 when Rowse, 49,
and DeBoer, 42, of Hazel Park sued to try to upset a law that bars them from
jointly adopting each other's children. But the case became even more
significant when Friedman invited them to add the same-sex marriage ban
to their lawsuit since adoption law for couples is tied to marriage.

The ban
was approved by 59 percent of voters in 2004. In her opening remarks, state
Assistant Attorney General Kristin Heyse stressed that the burden is on DeBoer
and Rowse to show the amendment is "irrational" under all possible
reasons.

"That's a very high bar, your
honor, and one plaintiffs can't meet," Heyse said.

She noted that the amendment was
widely embraced by voters - "not a whim of the few."

It is the first U.S. trial on a gay-marriage ban
since a trial in California in 2010,
said Dana Nessel, co-counsel for DeBoer and Rowse. Most legal challenges in
other states have been decided in other ways.

"We've seen different approaches
by different courts. ... I don't think you need to hear extensive evidence to
determine that these laws violate basic rights of equality," said Jennifer
Levi of Western New England University law school in Springfield, Mass., who
worked on a lawsuit that led to the legalization of same-sex marriage in that state in 2004.

Mark Regnerus, a sociologist at the
University of Texas, is among the state's witnesses. In 2012, he published a
study in an academic journal, saying young adults with a parent who had a
same-sex relationship were more likely to experience unemployment and other social
woes. He later acknowledged that his study didn't look at children raised by
stable same-sex couples.

Another witness is scholar Sherif
Girgis, author of a 2012 book, "What Is Marriage?
Man and Woman: A Defense." Attorneys for DeBoer and Rowse are asking the
judge to block their testimony as irrelevant.

On Monday, more than 30 pastors from
Baptist churches and conservative Christian congregations held a news
conference to declare their support for the Michigan
ban. They said family stability and the
Bible demand marriage only between a
man and a woman.